Mountain Biking UK Dec2012 issue has a powertap hub test...

of three identical weight carbon hardtails, 26"/650B/29er tired, on the same course, using the powertap to keep the power output of the rider in check as he does laps on a course. The bikes were a Felt Six Pro, Felt Nine Team, and a KHS SixFifty 609. They used water bottle ballast to get the bikes to the identical scale weights, and all ran Schwalbe Hans Damf 2.35 tires pumped to 25psi.

The course has a 3.3km uphill followed by a 3.7km downhill for a 7km total lap. The climbs were done with the power kept to an average of 227 wats (+/- 2 watts) and the downhill with no restriction on power, just on tire grip.

On the uphill section, the 26er scored 13:54, the 650B 13:41 and the 29er 13:39, and the downhill they were 7:58, 7:47 and 7:44 respectively. So overall the 26er was 21:52 for a lap, the 650B was 21:28, and the 29er was 21:23.

I don't post to generate business for myself or make like I'm better than sliced bread

I'd be interested to see pictures of the track in question. A rocky, rooty track may give more advantage to the 29er, while a smoother, flowly trail with jumps and drops may allow the 26/27.5 to catch up.

It'd would also be great to see the amount of movement in the steering or forces involved. I would venture to say that again, depending on the trail condition, we would see some interesting results. Likely the 26/27.5 would have lots of movement with not much effort, except in areas of rocks/roots, and the 29er would have lots of force required in technical or "jumpy" terrain.

Axe the OP said they used Ballasts in the Water Bottle to even the weight..........I have been trying to download the issue on the ipad but it won't download for some damn reason....

That was my point. They artificially increased weight on smaller sized bike. Hans Dampf on 26" is half a pound of weight less (90g per tire, 40g per rim) than on 29.
Just pointing this out - since we are doing a "scientific" comparison and stuff.

That was my point. They artificially increased weight on smaller sized bike. Hans Dampf on 26" is half a pound of weight less (90g per tire, 40g per rim) than on 29.
Just pointing this out - since we are doing a "scientific" comparison and stuff.

I get it; to even out the bike weights as they did they were 'weighting', as it were, the test results towards the larger wheel sizes.

I get it; to even out the bike weights as they did they were 'weighting', as it were, the test results towards the larger wheel sizes.

No this is inaccurate.....the smaller wheels were able to retain their lighter weight per wheel which makes a bike faster than a bike with heavier wheels, irregardless of a water bottle as a ballast or a top tube that weighs more between the bikes.....the lighter 'unsprung weight' is an ADVANTAGE on climbs and descents based on their methodology....acceleration and DECELERATION are both at an advantage for a lighter wheelset which in turn for what we do on a bike makes for a faster ride.

I finally got the issue to download and here are a couple of keys quotes that stood out to me:

"While there was no clear winner there was a clear loser: the 26in bike was the slowest on every single lap"

This is a pretty good article regardless of the camp each sits in......

That was my point. They artificially increased weight on smaller sized bike. Hans Dampf on 26" is half a pound of weight less (90g per tire, 40g per rim) than on 29.
Just pointing this out - since we are doing a "scientific" comparison and stuff.

Trying to "equalize" the test by making the bikes the same weight may seem like a good idea, but it is not valid for the real world. Part of the performance differences of the wheel sizes is the weight, not only in the tires, rims and spokes but the frames and forks. Nobody in a race is going to add weight to their bike because others have heavier bikes.

Use the same model frames, forks, rims and tires. Setup with the same components, similar final gear ratios, same rider fit and let the weights be what they naturally are. That is how the bikes are used.

No this is inaccurate.....the smaller wheels were able to retain their lighter weight per wheel which makes a bike faster than a bike with heavier wheels, irregardless of a water bottle as a ballast or a top tube that weighs more between the bikes.....the lighter 'unsprung weight' is an ADVANTAGE on climbs and descents based on their methodology....acceleration and DECELERATION are both at an advantage for a lighter wheelset which in turn for what we do on a bike makes for a faster ride.

I finally got the issue to download and here are a couple of keys quotes that stood out to me:

"While there was no clear winner there was a clear loser: the 26in bike was the slowest on every single lap"

This is a pretty good article regardless of the camp each sits in......

Wheels that can accelerate and decelerate faster does not mean the bike will always be faster. There are times when a wheel that maintains its speed is faster than one the decelerates easily, and not just on the flats or downhills. It is the whole package matters.

Trying to "equalize" the test by making the bikes the same weight may seem like a good idea, but it is not valid for the real world. Part of the performance differences of the wheel sizes is the weight, not only in the tires, rims and spokes but the frames and forks. Nobody in a race is going to add weight to their bike because others have heavier bikes.

Use the same model frames, forks, rims and tires. Setup with the same components, similar final gear ratios, same rider fit and let the weights be what they naturally are. That is how the bikes are used.

Agreed. The weight savings from 29er to 650b has the potential to make this "experiment" even closer.

Trying to "equalize" the test by making the bikes the same weight may seem like a good idea, but it is not valid for the real world. Part of the performance differences of the wheel sizes is the weight, not only in the tires, rims and spokes but the frames and forks. Nobody in a race is going to add weight to their bike because others have heavier bikes.

Use the same model frames, forks, rims and tires. Setup with the same components, similar final gear ratios, same rider fit and let the weights be what they naturally are. That is how the bikes are used.

Well, they did accurately measure that a larger diameter tire has less rolling resistance and better grip.

It does not address that you can fit more suspension with a smaller wheel, decrease weight and increase stiffness, fit smaller people etc. But all of that is difficult to test head to head.

Well, they did accurately measure that a larger diameter tire has less rolling resistance and better grip.

It does not address that you can fit more suspension with a smaller wheel, decrease weight and increase stiffness, fit smaller people etc. But all of that is difficult to test head to head.

My point is you test the wheels size/bikes for what they are and as they will be used rather than trying to make them identical in every other aspect.

MBUK presented this as a "real world" test. The bikes should be real world, too (they were close0. The only results presented is elapsed time. The Powertap meter was used only to have the rider maintain the same pedaling effort for each test ride. They measured that the larger wheeled bikes were faster. We can only theorize that it is because of differences in RR and grip as those factors were not directly measured.

This test was about wheel size, not suspension design, frame geometry, fit, or riding style.
You would not do it with a 29er rigid singlespeed, 120mm travel 650B and a 26" downhill bike. That would be interesting but useless for a wheel size comparison.
Let the "shootout" articles discuss the pros and cons of the different bike models and their intended use.

But I MUCH prefer real world testing to isolated lab tests despite the ambiguities.

I understand what they are trying to do equalizing all the bike weights which then isolates it down to just the wheel differences. It makes some sense to see it this way which is interesting but I agree with Shiggy, it's not a real world test and should be like he mentioned in post #12

Use the same model frames, forks, rims and tires. Setup with the same components, similar final gear ratios, same rider fit and let the weights be what they naturally are. That is how the bikes are used.

Since the 29'er wouldn't probably change in this test (being the heaviest) the other 2 would incrementally get a little closer I assume. Maybe the 26'er would close the gap on the 650? So terrain related also. Some places the 29'er will kill the other 2 and vice versa. All I know is 650B is the Swiss Army knife of wheel sizes IMHO.

But I MUCH prefer real world testing to isolated lab tests despite the ambiguities.

I do like lab tests - for what they are. When they actually measure fork or frame deflection, or tire energy losses, in isolation, in a controlled environment etc. Sometimes it is quite illuminating.

Is it mentioned there how tall the test rider is?

...Personally - after trying my friends 650b bike, and agreeing that it does make a lot of sense, I did not change my Nicolai to 650b. Preferred to keep 170mm on both ends, not 160mm, running a beefier tire and wheel for the same weight. Just feels more fun for this format and for my size. If I make a shorter travel, at around 140mm, lighter bike in the future, that I will setup with 650b. If I build a new hardtail or ~100mm full suspension, I would go with 29. Just my take on it.

I do like lab tests - for what they are. When they actually measure fork or frame deflection, or tire energy losses, in isolation, in a controlled environment etc. Sometimes it is quite illuminating.

But potentially not completely transferable to how it performs on the trail. Tire lab tests usually run the tire on a 1-1.5 meter diameter steel drum and hold the wheel in a firm vertical position. The closest I have come to riding a bike like that is on a wind trainer.

Any lab test needs to accurately reflect real world performance. That means conducting both types and comparing the results. Then adjusting the lab test procedures to have their results more closely match the actual performance.

Formula 1 race teams do this all the time. Recalibrating their wind tunnels and simulators to match the results they get on the track. Each team spends tens of millions on lab testing and they still get it wrong and go in directions that do not work in the races.

But potentially not completely transferable to how it performs on the trail. Tire lab tests usually run the tire on a 1-1.5 meter diameter steel drum and hold the wheel in a firm vertical position. The closest I have come to riding a bike like that is on a wind trainer.

In some sense weighting your bike on a stand is a lab test. And on a local fireroad climb I use for training/timing - 10 extra pound on a bike pretty much mean to me I have to ride it a gear lower. But then, extra 10 deg of temperature has the same effect on me.

One can't just use such a test, run by one particular rider, and then publish a article proclaiming a "clear loser". That seems like bollocks. At the very least they should not have artificially make the weights equal. They are not.

In some sense weighting your bike on a stand is a lab test. And on a local fireroad climb I use for training/timing - 10 extra pound on a bike pretty much mean to me I have to ride it a gear lower. But then, extra 10 deg of temperature has the same effect on me.

One can't just use such a test, run by one particular rider, and then publish a article proclaiming a "clear loser". That seems like bollocks. At the very least they should not have artificially make the weights equal. They are not.

Simply weighing a bike is not a performance test. Doing something to measure the effect of a given weight change is.

MBUK's test did use a very limited data pool. I would have liked to see at least twice as many laps and thrown out the fastest and slowest lap and/or any lap with some sort of issue. If they used additional riders, each of them would have to ridden the same number of laps. I would have then used the averages of each rider for the overall results.

But within the results of the test they did perform (the procedures of which were mostly OK) there was a "clear loser."

I said a "test", not a "performance test". It is a clear test with very exact implications.

I think there was not, precisely for the reasons you have mentioned. "Clear loser" implies statistical significance and broad implications of the result.

Your weight "test" (a misuse of the term, as "performance test" is redundant. Weighing something is just a measurement.) is making a bigger assumption than the MBUK test. "Implication" means it have not actually been tested or proven, just suggested from other data.

At least MBUK has actual, if incomplete, data. But within the results of the test they did perform(the procedures of which were mostly OK) there was a "clear loser," even if we find flaws in the test.

Your weight "test" (a misuse of the term, as "performance test" is redundant. Weighing something is just a measurement.) is making a bigger assumption than the MBUK test. "Implication" means it have not actually been tested or proven, just suggested from other data.

Effect of weight on climbing is understood as well as pretty much anything else measurable on a bicycle. It has been tested and proven and has trivial physics behind it. Not sure what's to debate there.

Originally Posted by shiggy

At least MBUK has actual, if incomplete, data. But within the results of the test they did perform(the procedures of which were mostly OK) there was a "clear loser," even if we find flaws in the test.

Actual data does not mean squat if you can not draw a reliable statistical conclusion from it. I am faced with this fact daily on my job.

P.S.
Some random google quote:

A cyclist weighing 72 kg rode several times a climb of 1 km (105m of difference in height) at increasing average wattages (from 280w up to 400w).
He repeated the same stretch at the same average power outputs, with the addition of 4 kg of scuba weights in his rear jersey pockets.

As we can see from the tab above, the influence of weight is greater when the speed (Vel) is low, probably because of the longer "dead spot" in the pedaling, which translates into a greater deceleration of the cyclist and a subsequent costly acceleration of the body mass.

Here's the thing - nobody is going to spend the money/time/effort to do a true double-blind, statistically significant test. This is among the better tests I've seen, along with:
Matt's: Revisiting the Rancor: 26 v. 29
Mike McCalla's was in Mountain Flyer #23, not sure if it can be seen online.

Nobody has done the kind of work you'd need to get published in Nature or something, but realistically nobody is going to do that, so while it's fine to criticize these guys, this is probably the best data we're ever going to get.

Here's the thing - nobody is going to spend the money/time/effort to do a true double-blind, statistically significant test.
-Walt

Of course. The only thing we know by now is that for a normal person the "performance", difference as measured in some arbitrary lap times, is probably not significant enough to worry about, so they should probably just ride whatever fits and whatever feels good.

For my completely personal preference, 29r hardtail rides much, much nicer, but long travel 29rs just do not feel as they fit well, and I like some suspension travel. Obviously YMMV.

From a guy that rides a 26" bike, who has never seen the point of anything else, I am starting to wonder why I am ridding a 26" bike. If a 27.5 or a 29 is faster going up and faster coming down, well, I just feel stupid...

I think the the 27.5 wheel will be the death of the 26 inch wheel, and the 29 inch wheel will be the death of the 27.5 inch wheel.

From a guy that rides a 26" bike, who has never seen the point of anything else, I am starting to wonder why I am ridding a 26" bike. If a 27.5 or a 29 is faster going up and faster coming down, well, I just feel stupid...

That test did not show it. 26" bike had been made artificially heavier. And it does not account for suspension.

Effect of weight on climbing is understood as well as pretty much anything else measurable on a bicycle. It has been tested and proven and has trivial physics behind it. Not sure what's to debate there.

Actual data does not mean squat if you can not draw a reliable statistical conclusion from it. I am faced with this fact daily on my job.

P.S.
Some random google quote:

I agree that increased weight is known to affect climbing speed/efficiency, but to call measuring the weight of a bicycle a test of that is just wrong. Nothing has been tested in regards to that bike.

You keep ignoring the "...within the results of the test..." We see the limitations of the procedure, and it is still better than any other published comparison. MBUK could have raised the related questions after their conclusions.

You keep ignoring the "...within the results of the test..." We see the limitations of the procedure, and it is still better than any other published comparison. MBUK could have raised the related questions after their conclusions.

Within the results of the test (artificially heavier bike and lack of data) one can not draw a blank conclusion that they did.

Well, whatever. A popular magazine did not follow a published study standard. Earthshaking. Stop the presses.

Except MBUK did mostly follow experimental procedures.
And those test procedures are much more involved than just measuring a single aspect--such as weight--of a bike.

Following an experimental procedure does not equate to obtaining a meaningful result. Making a complicated measurement does not improve the measurement quality over a simple measurement, most often it would be the opposite.

I guess since I am repeating this in the Nth time it was not clear, so I would rather stop trying. (And I would not want to descend into a pissing contest on whether I am qualified to talk about experimental procedures..) Done here.

Looking at the full results for each lap, the 650B was fastest uphill on 3 of the 4 laps, but the 1 lap where the 29er was the fastest caused its average to be the fastest for the uphill.

For the downhill part, the 29er was fastest on 3 of the 4 laps, with the 650B being the 2nd fastest on those 3 and the fastest on the remaining lap.

Next, looking at the fastest overall times, both the 650B and the 29er achieved a 21:17 time (29er got 21:16, and that could be measuring error), but the fastest lap on the 26 inch was 21:38.

While it isn't statistically significant and there are, as others have pointed out, other complications, I found the above to be very interesting and tends to support the notion that the 650B has the benefit of the 29er wheel size, but remains more nimble.

Following an experimental procedure does not equate to obtaining a meaningful result. Making a complicated measurement does not improve the measurement quality over a simple measurement, most often it would be the opposite.

I guess since I am repeating this in the Nth time it was not clear, so I would rather stop trying. (And I would not want to descend into a pissing contest on whether I am qualified to talk about experimental procedures..) Done here.

Well, you seem to be misunderstanding my points as much as you think I am misunderstanding yours.

Looking at the full results for each lap, the 650B was fastest uphill on 3 of the 4 laps, but the 1 lap where the 29er was the fastest caused its average to be the fastest for the uphill.

For the downhill part, the 29er was fastest on 3 of the 4 laps, with the 650B being the 2nd fastest on those 3 and the fastest on the remaining lap.

Next, looking at the fastest overall times, both the 650B and the 29er achieved a 21:17 time (29er got 21:16, and that could be measuring error), but the fastest lap on the 26 inch was 21:38.

While it isn't statistically significant and there are, as others have pointed out, other complications, I found the above to be very interesting and tends to support the notion that the 650B has the benefit of the 29er wheel size, but remains more nimble.

I just rode a 650b today and did some nasty little climbs in the super wet leafy mess and my 650b climbed well enough for me......Your analysis above is APPRECIATED, I didn't breakdown the actual laps, thanks!

Except MBUK did mostly follow experimental procedures.
And those test procedures are much more involved than just measuring a single aspect--such as weight--of a bike.

They TRIED to do a scientific test, but despite getting some aspects correct they failed on others.

They did use all the same tires at the same pressure and same overall weight. However that is not quite right.

Same tire = good.
Same weight = good and bad. The issue is that wheel & tire weight is a factor in how these wheels perform so ballasting all bikes to 25lbs for example does not take into account the extra weight needed for 29" wheel and possible extra weight needed for frame geometry. What they should have done is to used the same Mfg with the same frame in all 3 sizes. (or as close as practicable).

Did they use 1 rider or multiple? Best to used multiple riders to try to cancel out the effects the rider as much as possible. How about rider fatigue? or Riders "learning the trail" or picking different lines for each bike.

Terrain? how mixed and varied. Mtn biking is not just climb and descent, but also turns/rocks/roots etc.

In the end scientific testing can be performed, but it will take a lot of work to do it just right. Even then once you must consider what happens when you move from hardtail to 3-4" FS to longer travel and slacker HAs?

Even then for most riders 30 seconds over a 20 min ride is not big deal. Unless you racing there is more variation that will occur with in a group ride to make difference. For most of us the issue comes down to feel more than anything. The issue is that feel is very subjective.

From one Joe to another......your idea that the 29er wheels need more weight makes no sense to me and doesn't compute to actual riding physics which benefits from Lighter wheels (stronger isn't the discussion point I'm making but yes that too), can you explain why you believe that part of your statement? Basically I need to be educated possibly.

From one Joe to another......your idea that the 29er wheels need more weight makes no sense to me and doesn't compute to actual riding physics which benefits from Lighter wheels (stronger isn't the discussion point I'm making but yes that too), can you explain why you believe that part of your statement? Basically I need to be educated possibly.

29" is larger than 26". So the tire, rim and spoke area all larger. More material = more weight. This is assuming identical construction and neglecting any stiffness issues. Now I am not saying you can't get 29" stuff lighter than 26", but that is because they are not the same material and/or construction.

Also a 29er frame will be heavier than 26" frame due simply to chainstay length again with same material and construction. It is minor in grand scheme of things, but it is a fact. It just the same way that a XL frame will be heavier than Small frame. One is larger and needs more material.

Point is that of the bikes 26" will be lighter than 27.5 and lighter than 29 if you use all the same parts and same material and construction. Ballasting the 26 to make it has heavy as a 29 is removing one advantage the 26er has. The potential to be lighter.

From one Joe to another......your idea that the 29er wheels need more weight makes no sense to me and doesn't compute to actual riding physics which benefits from Lighter wheels (stronger isn't the discussion point I'm making but yes that too), can you explain why you believe that part of your statement? Basically I need to be educated possibly.

I think basically he's saying to make a 29'er (rims, tires, frame) adds some additional weight in all 3 areas over the exact same 650 or 26" built identically. Not you "need" to add weight.

I get why they did what they did but it's still not real world and in the end the 650 and 26" were handicapped by ballast weight.

If all the parts EXCEPT those related to wheel size are controlled, then it works, but as mentioned, to add weight when part of the advantage of a comparable 26" wheel is it's lighter weight, then they are missing the mark. Same thing applies to a frame or fork.

IMHO, of course.

I actually read MBUK regularly, and think it is as good a mtb mag as their is.

Your testing methodology is fairly sound.
It is possible to create a scientific valid study to figure to identify variables and control for them when it comes to wheelsize. I've yet to see anything that is actually publishable in a peer-reviewed journal. We've heard of internalized testing from organisations like Scott, but I don't think we any "official" numbers on this stuff yet.

Perhaps I should go beg or borrow a couple of powertap hubs(or a few srm) and get identical product out of our sponsors for three bikes...
I bet someone can track down some bike geek exercise scientist at some university that's looking for a thesis project.

At some point people are going to need to produce some hard numbers on wheelsize, because right now we're all essentially talking out of our a%ses.

Your testing methodology is fairly sound.
It is possible to create a scientific valid study to figure to identify variables and control for them when it comes to wheelsize. I've yet to see anything that is actually publishable in a peer-reviewed journal. We've heard of internalized testing from organisations like Scott, but I don't think we any "official" numbers on this stuff yet.

I am sure the big mfg and possibly the weld funded XC race teams have done some very scientific testing. However that testing costs money and they would probably rather keep the results (especially the details) to themselves.

Designing a test is easy. What is hard it getting funds to obtain all the bikes needed to it right. Then you need time and riders.

Dirt mag did a test with 2 Enduro riders, some months ago.
I think it was compared ramblefish vs remedy and a tracer 29r vs Carbide (I think it were the models used).
With first rider it could be seen he was a bit faster on the 26.
The second rider was really faster on 29er and the worst time was better than the best time from the first rider.

Like some have already asked/said- fun cannot be measure cientenficaly (almost like love...)

Strava "told me" I was fastest on a stumpy expert carbon 29 than my old intense 6.6 or c'dale rize.
I had a lot of fun, and would swap that day my 2 rides+ money for that bike....
After some thinking, I felt quicker and that was the fun part. But the Fun wasn't there...

Just a side note
It's almost like comparing 4wd with rwd.
4wd will be in most situations faster/safer/confidence inspirer than rwd.
But I do prefer rwd, even with lower power. It's must more Fun.

For those saying the 26" was handicapped, I'd say it might be the other way around - the 29er may have been handicapped.

Here's why...

A HD is a lot of tire for a 29er. Most experienced 29er riders will tell you to get the same trail "control" from a 29" tire compared to it's 26" equivalent, you'd downsize the tire width on the 29er. For example, you might get the same feel on a 2.2 x 29 as you would on a 2.35 x 26 tire. Climbing on a 2.35 x 29 HD would likely be a chore, and overkill for all but the most technical climbs. On the downhill, the fatter rubber would likely lend an advantage, but even then not that much. With that said, the 29er was at an unfair advantage on the climbs.

I do agree it was unfair to weigh down the smaller wheeled bikes. The fairest test, IMO, would to build "equally capable" bikes for your average trail/course. That might mean something like a 26" bike with 5.5" of travel and 2.35" tires. A 650b with 5" of travel and 2.2" tires. A 29er with 2.1" tires and 4" of travel. You'd likely get those bikes weighing in close to each other. Have a number of experienced riders do several runs on each to be sure all bikes felt equally capable in terms of feeling "in control" on the trail. Then do the timed laps to see which was the fastest (not necessarily the "funnest"). You'd likely find that some wheel sizes do better on different trail types. But, overall I'd bet the 26" bike would likely be the slowest. Human horsepower is the weakest link. Rolling resistance hits that weak link. A design that alleviates that weak link, such as a larger wheel, will likely come out ahead. Admittedly there is likely a point of diminishing returns where variables like overall wheel weight and wheel stiffness start to negate the benefits of larger diameter wheels. Where that is, I don't know... with current technology, probably somewhere around the 650b or 29er.

Lastly, in terms of unfair bias, the longer a course the more impact a more stable, smooth, design will have. For example, for years I rode rigid SS on very rough trails side by side with very experienced riders on 5-6" travel trail bikes. Often, I was faster for the first hour or so. After that the full body fatigue of managing such an "unstable" albeit, light and efficient, bike took its toll, and I became much slower as the ride went on. Pretty much folks who race xc can tell you that often they are faster on the HT on short courses, but anything beyond an hour or so they'll be faster on a FS. (Elite level racers may be different or find they fatigue on the HT after 2 or 3 hours.) Thus, the more stable, less draining, albeit less snappy, larger wheeled bike would likely have the advantage on a test course of longer length.

After riding all three wheel sizes on everything from XC to AM I've found little use for the 26" (I no longer strictly DH). For xc to trail its a 29er. For trail to AM its a 650b. This factors in both speed and fun.

Folks get very bent and defensive when tests compare different bikes and wheel sizes and use lap times and speed as a measure. Yes, speed and fun are two different things. But, speed is a surrogate for efficiency. The more efficient a design the longer and faster you can ride. The more energy you have left over to hit the jumps. And, most importantly, to dust your buds and be king-o-the-hill